I recently converted my car from a t56 to a th-400. I was just wondering if anyone knows how to get the speedo to work. I got the wires hooked up but its way off. it says im doing like 80 when im doing around 30. Does anyone know how to fix this? Thanks

 

I'm going to a 400 very soon myself, kind of wondering the same thing. As far as I know, you have to change the plastic gear in the sensor. There is some math that has to be done to find out which one you will need. Hope this helps.

 

You need a GM sensor and reluctor wheel. Sensor is part # 8655315 and the reluctor is 8655291. Depending on your set-up this will get you close. You may have to adjust gear or tire size in the PCM to fine tune it.